[gnome-ostree] Only rebuild initramfs if certain components change

[Colin Walters <walters src gnome org>]

commit 08f5ebb113199877815a9f2eb7dcc0563de21a02
Author: Colin Walters <walters verbum org>
Date:   Sun Apr 7 15:47:14 2013 -0400

    Only rebuild initramfs if certain components change
    
    Beyond simple speed, this avoids a 15MB blob being stored per build,
    and downloaded by every client on every update.

 manifest.json              |    4 ++++
 src/js/tasks/task-build.js |   44 +++++++++++++++++++++++++++++++++++++++++---
 2 files changed, 45 insertions(+), 3 deletions(-)
---
diff --git a/manifest.json b/manifest.json
index 66e1339..75dab60 100644
--- a/manifest.json
+++ b/manifest.json
@@ -619,6 +619,7 @@
                 "config-args": ["--disable-tls-check"]},
 
                {"src": "gnome:ostree",
+                "initramfs-depends": true,
                 "config-opts": ["--disable-documentation",
                                 "--with-soup-gnome"]},
 
@@ -816,6 +817,7 @@
                 {"src": "git:git://git.kernel.org/pub/scm/boot/dracut/dracut.git",
                 "config-opts": ["--disable-documentation",
                                 "--enable-systemd"],
+                "initramfs-depends": true,
                 "tag": "ae4758ce0d0ceeddabe4a78dd575c7b42c349a88",
                 "patches": ["dracut-Support-OSTree.patch",
                             "dracut-systemd-configure.patch"]},
@@ -847,6 +849,8 @@
 
                {"src": "gnome:gnome-software"}
        ],
+
+    "initramfs-build-epoch": {"version": 0},
     
     "build-epoch": {"version": 8,
                    "all": true,
diff --git a/src/js/tasks/task-build.js b/src/js/tasks/task-build.js
index dc6b2ca..94dce79 100644
--- a/src/js/tasks/task-build.js
+++ b/src/js/tasks/task-build.js
@@ -722,7 +722,7 @@ const TaskBuild = new Lang.Class({
        return [treename, ostreeRevision];
     },
 
-    _generateInitramfs: function(architecture, composeRootdir, cancellable) {
+    _generateInitramfs: function(architecture, composeRootdir, initramfsDepends, cancellable) {
        let e = composeRootdir.get_child('boot').enumerate_children('standard::*', 
Gio.FileQueryInfoFlags.NOFOLLOW_SYMLINKS, cancellable);
        let info;
        let kernelPath = null;
@@ -740,6 +740,31 @@ const TaskBuild = new Lang.Class({
        let releaseIdx = kernelName.indexOf('-');
        let kernelRelease = kernelName.substr(releaseIdx + 1);
 
+        let initramfsCachedir = this.cachedir.resolve_relative_path('initramfs/' + architecture);
+       GSystem.file_ensure_directory(initramfsCachedir, true, cancellable);
+
+       let initramfsEpoch = this._snapshot.data['initramfs-build-epoch'];
+       let initramfsEpochVersion = 0;
+       if (initramfsEpoch)
+           initramfsEpochVersion = initramfsEpoch['version'];
+       let fullInitramfsDependsString = 'epoch:' + initramfsEpochVersion +
+           ';kernel:' + kernelRelease + ';' +
+           initramfsDepends.join(';'); 
+       let dependsChecksum = GLib.compute_checksum_for_bytes(GLib.ChecksumType.SHA256,
+                                                             GLib.Bytes.new(fullInitramfsDependsString));
+
+       let cachedInitramfsPath = initramfsCachedir.get_child(dependsChecksum);
+       if (cachedInitramfsPath.query_exists(null)) {
+           print("Reusing cached initramfs " + cachedInitramfsPath.get_path());
+           return [kernelRelease, cachedInitramfsPath];
+       } else {
+           print("No cached initramfs matching " + fullInitramfsDependsString);
+       }
+
+       // Clean out all old initramfs images
+       GSystem.shutil_rm_rf(initramfsCachedir, cancellable);
+       GSystem.file_ensure_directory(initramfsCachedir, true, cancellable);
+
        let cwd = Gio.File.new_for_path('.');
        let workdir = cwd.get_child('tmp-initramfs-' + architecture);
        let varTmp = workdir.resolve_relative_path('var/tmp');
@@ -765,7 +790,9 @@ const TaskBuild = new Lang.Class({
 
        GSystem.file_chmod(initramfsTmp, 420, cancellable);
 
-       return [kernelRelease, initramfsTmp];
+       GSystem.file_rename(initramfsTmp, cachedInitramfsPath, cancellable);
+
+       return [kernelRelease, cachedInitramfsPath];
     },
 
     /* Build the Yocto base system. */
@@ -1065,9 +1092,20 @@ const TaskBuild = new Lang.Class({
            let develTargetName = 'buildmaster/' + architecture + '-devel';
            let develTarget = this._findTargetInList(develTargetName, targetsList);
 
+           // Gather a list of components upon which the initramfs depends
+           let initramfsDepends = [];
+           for (let j = 0; j < components.length; j++) {
+               let component = components[j];
+               if (!component['initramfs-depends'])
+                   continue;
+               let archname = component['name'] + '/' + architecture;
+               let buildRev = componentBuildRevs[archname];
+               initramfsDepends.push(component['name'] + ':' + buildRev);
+           }
+
            let [composeRootdir, relatedTmpPath] = this._checkoutOneTree(develTarget, componentBuildRevs, 
cancellable);
            
-           let [kernelRelease, initramfsPath] = this._generateInitramfs(architecture, composeRootdir, 
cancellable);
+           let [kernelRelease, initramfsPath] = this._generateInitramfs(architecture, composeRootdir, 
initramfsDepends, cancellable);
            archInitramfsImages[architecture] = [kernelRelease, initramfsPath];
            let initramfsTargetName = 'initramfs-' + kernelRelease + '.img';
            let targetInitramfsPath = 
composeRootdir.resolve_relative_path('boot').get_child(initramfsTargetName);